Reinforcing bars having depressed portions for use in concrete constructions



Jan. 27, 1959 J. GILLBE RG 2,879,626

REINFORCING BARS HAVING DEPRESSED PORTIONS FOR USE IN CONCRETE CONSTRUCTIONS Original Filed Nov. 3, 1950 2 Sheets-Sheet 1 J. GILLBERG Jan. 27, 1959 2,870,626

RE ING BARS HAVING DEPRESSED PORTIONS USE IN CONC ETE CONSTRUCTIONS orlglnal Flled Nov 50 2 Sheets-Sheet 2 United States Patent REINFORCING BARS HAVING DEPRESSED POR- TIONS FOR USE IN CONCRETE CONSTRUC- TIONS Johannes Gillberg, Stockholm, Sweden Original application November 3, 1950, Serial No. 193,862. Divided and this application February 9, 1956, Serial No. 564,528

Claims priority, application Sweden November 4, 1949 6 Claims. (Cl. 72-111) An object of the invention is to provide depressed portions in the reinforcing bars so as to prevent the bars from creeping in the concrete as well as other desirable properties fully described hereinafter. It has previously been suggested to provide projections of various types on reinforcing bars, the desired profiled shape of the bars being obtained by rolling the bars in a hot state. The present invention is distinguished by the fact that shoulders or depressions of predetermined shape and dimensions are formed in the reinforcing bar by making depressions in the bar in a cold state thereof by compressing the material of the bar at the places of depressions. This results in a number of advantages. In the known manufacture of bars provided with projections by rolling in a hot state, the core diameter or smallest cross-sectional area of the bar has to be dimensioned in accordance with the tensile stresses to which the bar is subjected in use. The projections on the bar consequently increase the weight without increasing the tolerable tensile stresses on the bar. In a reinforcing bar manufactured in accordance with this invention, in which the projections of predetermined shape and dimension are formed by depressing parts of the bar, the tensile stresses can be calculated for the largest cross-sectional area of the bar, since the reduction of the cross-sectional area due to the depressions is a result of the compression of the material resulting in a corresponding increase of the tensile strength. Thepresent invention consequently saves material.

A further object of the invention is to provide simple, efiicient and economical means for transforming a usual round reinforcing metal bar to one in which its tensile strength is improved simultaneously as the anchoring of the metal bar in the concrete is improved.

In the accompanying drawings, there are illustrative examples of reinforcing bars manufactured in accordance with this invention.

Figure 1 is a view of a reinforcing bar constructed in accordance with this invention,

Figure 2 is a cross-sectional View taken on line II-II of Figure I,

Figure 3 is a cross-sectional view taken on line III-III of Figure 1,

Figure 4 is a view of a modified construction of a. reinforcing bar made in accordance with this invention,

'Figure 5 is a cross-sectional view taken on line VV of Figure 4, V

' Figure 6 is a cross-sectional view taken on line VIVI of Figure 4,

Figure 7 is a view of. still another modified construc- 2,870,626 Patented Jan. 27, 35 9 2 tion of a reinforcing bar made in accordancewith this invention, I

Figure 8 is a cross-sectional view taken on line VIlI-VIII of Figure 7,

Figure 9 is a cross-sectional view taken on line IXIX of Figure 7,

Figure 10 is a fragmental longitudinal sectional view of an apparatus for forming depressions in a metal bar in accordance with this invention,

Figure 11 is a tranverse sectional view of the apparatus shown in Figure 10, and

Figure 12 is a fragmental side view of the apparatus for forming a reinforcing bar having the construction shown in Figure 7. a

In the drawings, reference numeral 1 denotes part of an iron bar having a circular cross-section as shown in Figure 2. To the right in Figure l, the metal bar is illustrated in its original form in which it leaves a hot rolling mill. By means of suitable apparatus, spaced depressions 2 and 3 are made in the body of the metal bar. These depressions are made in the cold state of the bar so as to obtain a compression of the material resulting in an increase of the tensile strength at the places of depression. Due to the depressions, shoulders 4 are formed at the places between the depressions and the sections which are maintained in their original shape. In the example illustrated in Figures 1-3, sections 5 are left between the depressions which are located at. equal distances from each other longitudinally of the bar. The distance 1 between adjacent depressions 2 or 3 is pre-, determined in accordance with special requirements, but generally said distance should be smaller than six times the diameter of the metal bar and preferably smaller than four times said diameter. The length a of the depression is between 0.3 and twice the diameter of the metal bar, and the length b of the intermediate portion is between 0.2 and twice said diameter.

As shown in Figure l the depressionsl and 3 are located in opposite relation to each other on opposite sides of the reinforcing bar. As will appear from Figure 3, the depressions are convex and extend only over a portion of the width of the bar and smoothly merge into the lateral undepressed portions 6.

The depth of the depressions is predetermined'from 3 to 25%, preferably between 6 and 12% of the diameter of the original bar as viewed in the direction of depression.

In the form of construction illustrated in Figures 4-6, the depressions 7 on opposite sides of the m'etal'brar are arranged in staggered relation. In this case, too, the lengths of the depressions 2 and 3 may vary in relation to the lengths of the intermediate non-depressed surfaces 6 of the metal bar. The outline of this bar has the general shape of zigzag or wave lines. According to the embodiment illustrated in Figures 7-9, the metal bar in addition to the curved depressions 7 is given a corrugated, sinuous or zigzag-like shape. In this case, the depressions 7 are located in staggered relation in the concave portions or valleys of the waveforms on opposite sides of the bar. The distance between ad jacent depressions on the same side of the bar should be between 1.5 and six times, preferably between 2.5 and 4.5 times the diameter of the bar. It will also be evident from Figure 7 that the depth of the waves of thesinuous shaped bar is so dimensioned in relation to the diameter of the bar that no part of the outline of the waves touches they produce a substantial compression of the material,

which compression together with bending of the bar alternately in opposite directions results in an increase of the tensile strength of the material. The reinforcing bars need not'bemanufactured-in the rolling mill, but may be given their final shape at the place of use or at the factory. The bars may be supplied in bundles. For instance, a common metal bar having a circular cross-section and a diameter of between A" and 1" may be wound so as to form an annular coil or bundle. Such bundles can be transported in a more Simple and cheaper way than the usual straight reinforcing bars. The bundle may be mounted on a roll from which it is unwound and supplied to a suitable device in which the metal bar is provided with the depressions previously described. j v

' In Figures and 11, there are illustrated deformation members for making depressions of the type shown in Figures 1' and 4. Two wheels or disks 8 and 9 are mounted on'shafts 10 and 11, respectively. By means 'of pins 12, the wheels 8 and 9 aresecured to gear wheels 13 and 14' having intermeshing teeth 15. In circular recesses 16 at the periphery of the wheels Sand 9 there are provided transverse projections 17 which during the, rotation of the wheels perform the depressions 2 and 3 in the metal bar 1. The metal bar can be moved either by means of a force acting in the direction of the arrow p or by having the deformation members 8 and9 together with a straightening device for the metal bar and the supply roll for the bar supported by a frame, runner 'or similar member which'is moved towards the right as viewed in Figure 2, while the metal bar is main-.

'tained in a fixed position. According to the construction described below, the gear wheels 13 and 14 are positively driven so as to actuate the wheels 8 and 9, the metal bar being moved forward on account of its engagement with the projections 17.

" If the wheels 8 and 9'are displaced angularly relative to";each other, the form of construction shown in Figure 4 or intermediate forms can be manufactured in the same machine.

The wheels 8 and 9 can be easily exchanged for other wheels so that various types of different shapes with regard to depth and length of the depressions can be manufactured.

In Figure 12 there are illustrated wheels 18 and 19, which are particularly suitable for effecting a slight corrugation of the metal bar in addition to be curved depressions in the material. The wheels have radial projections 20 of smooth curved form for effecting the curved depressions, and recessed portions 21 between the projections. As will appear from the drawing, the metal bar will be slightly bent due to the fact that it rests against two projections 20 while another projection is making a depression at a place between said two projections. The metal bar will thus be alternately bent up and down while being fed between the two wheels to impart a sinuous or wave shape thereto.

' It will be understood that the depressions, as viewed in a lateral direction of the bar, are given a smooth curved shape having no rupture initiating'points. The depressions as well as the slight corrugations of the metal will improve the fasteningof the bar to the concrete.

The depth of the depressions vary between 3% and 25%, preferably between 6 and 12% of the diameter of the metal rod.

- Itwill be observed that an essential feature of this fabrication is that the tooth of the rotary member 18 abuts against one side of the bar 1 while the other side of the bar is supported by two of the teeth 20 spaced on: opposite sides of the tooth so that the bar as it 'is fed longitudinally between the rotary members abuts against the teeth and is not pressed to be forced into the root or space between the adjacent teeth." By this means the bar is alternately bent upwardly and down wardly or in opposite directions. This bending has the surprising effect of causing the metal bar between the corrugated portions to become substantially straight even though the bar has previously been bent. This bending of the metal bar alternately upwardly and downwardly involves,'in reality, a simultaneous working of the bar and results in a substantial increase in the tensile strength of the metal bar. Further, these slight corrugations and the depressions 7 provide means for improving the fastening or anchoring of the metal bar in the concrete.

It has been found that the metal bar, while being curved as-it is unwound from aroll, becomes substantially straight except for its corrugation as it leaves the wheels 18 and 19 this being a result of the bending of the bar in either direction when the depressions 7 are produced in the metal bar.

It is to be understood that many modifications and changes may be made in the construction of the reinforcing bars as described and that such modifications are intended-to be included within the scope of the appended claims.

Iclaim:

1. A reinforcing iron bar subject to tensile stressesand for use in concrete constructions formed of an elon-. gated iron body having substantially circular cross sectional contour and being bent into a regular wave form, said barhaving cold-compressed depressions in each of the valleys ofthe said waveform, the cross-sectional area of the bar being reduced at said depressions, the depressions on one side of the bar being staggeredrelative to the depressions on the opposite side of the bar, said depressions having a substantially uniform and smoothly curved shape compensating the reduction of the cross sectional area of the bar at the places for the said depressions by increasing the yielding point of the iron bar at the place of the said depressions.

2. A reinforcing iron bar subject to tensile stresses and for use in concrete constructions formed of an elongated iron body having substantially circular cross-sectional contour and being bent into a regular wave form, said bar having cold-compressed depressions in each' of the valleys of the .said waveform, the cross-sectional area of the bar being reduced at said depressions, the depressions on one side of the bar being staggered relative to the depressions on the opposite side of the bar, said depressions having a substantially uniform and smoothly curved shape compensating the reduction of the cross sectional area of the bar at the places for the said depressions by increasing the yielding point of the iron bar at the place of the said depressions and not extending beyond the central longitudinal axis of the bar.

3. A reinforcing iron bar subjectto tensile stresses and for use in concrete constructions formed of an elongated iron body having substantially circular cross-sectional contour and being bent into a regular wave form, the cross-sectional'area of the bar being reduced atsaid depressions, said bar having cold-compressed depressions in each of the valleys of the said wave form, the depressions on one side of the bar being staggered relative to the depressions on the opposite side of the bar, said depressions having a substantially uniform .and smoothly curved shape, the depth of said depressions being between 3% and 25% of the circular diameter of the uncompressed bar and spaced from each other on the same side of the bar at a longitudinal distance of less than 6 times the circular diameter of the bar, compensating the reduction ofv the cross sectional area of. the bar at the places for the said depressions by increasing the yielding point of the iron bar at the place of the said depressions.

4. Areinforcing iron bar as defined in claim '1 wherein the distance between adjacent depressions on the same 5. A reinforcing iron bar as defined in claim 1 wherein the longitudinal length of the depressions is between 0.3 and 2 times the circular diameter of the uncompressed bar and the length of the portions intermediate the de pressions is between 0.2 and 2 times the circular diameter 5 of the bar. 7

6. A reinforcing iron bar as defined in claim 1 wherein the depressions extend toward the longitudinal axis of the bar from 6 to 12% of the circular diameter of the uncompressed bar. 10

References Cited in the file of this patent UNITED STATES PATENTS 691,416 Thacher Jan. 21, 1902 15 6 Riser Feb. 25, 1902 Slick Mar. 17, 1908 Baum Dec. 28, 1909 Schuster Sept. 12, 1922 Abramsen Sept. 28, 1926 Wise Apr. 27, 1937 Scott Apr. 2, 1940 Norkin Q. June 17, 1952 FOREIGN PATENTS Great Britain 1907 

